Electron microscopic investigation of germinating Petunia pollen has yielded new data concerning fine structure of the pollen tube wall and of the rotoplasm. The cell wall reveals two layers, an inner one containing cellulose microkbrils, embedded in a matrix, and an outer one consisting of acid resistant material. The multi-net growth theory is applicable to the growth of the pollen tube.Round the generative nucleus, there is a generative cytoplasm containing organelles. This cytoplasm is separated from the vegetative cytoplasm by a cell wall-like structure. So we ought to speak of a generative cell. The vegetative nucleus is lobed and is surrounded by a nuclear envelope containing pores.The Golgi apparatus produces vesicles which accumulate in the tip of the pollen tube and probably have a function in building up the cell wall.

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The differentiation of the transmitting tissue of the style of Petunia hybrida was investigated with the electron microscope. The cells of this tissue are surrounded by an intercellular substance. The same holds true for a number of styles of other investigated species. This intercellular substance may not be compared with a middle lamella. The earlier suggestion, that the transmitting tissue of solid styles is collenchymatic in nature, is rejected.

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